<template>
  <div>
      <ul class="list">
          <li class="item" 
          v-for="item in letters" 
          :key="item" 
          @click="handleLetterClick"
          @touchstart="handleTouchStart"
          @touchmove="handleTouchMove"
          @touchend="handleTouchEnd"
          :ref="item"
          >
          {{item}}</li>
      </ul>
  </div>
</template>

<script>
export default {
    props:{
        cities:Object
    },
    data(){
        return{
            touchStatus:false,
            StartY:0,
            timmer:null
        }
    },
    updated(){
        this.StartY= this.$refs['A'][0].offsetTop
    },
    computed:{
        letters(){
            const letters =[]
            for(let i in this.cities){
                letters.push(i)
            }
            return letters
        }
    },
    methods:{
        handleLetterClick(e){
            // console.log(e.target.innerText);
            this.$emit('change',e.target.innerText)
        },
        handleTouchStart(){
            this.touchStatus=true
        },
        handleTouchMove(e){
            if(this.touchStatus){
                if(this.timmer){
                    clearTimeout(this.timmer)
                }
                this.timmer=setTimeout(()=>{
                    // const startY = this.$refs['A'][0].offsetTop
                    // console.log(this.StartY);
                    const touchY =e.touches[0].clientY-79
                    const index =Math.floor((touchY-this.StartY)/20)
                    console.log(index);
                    if(index>=0&&index<this.letters.length){
                        this.$emit('change',this.letters[index])
                    }
                },16)
                
                
            }
        },
        handleTouchEnd(){
            this.touchStatus=false
        }
    }
}
</script>

<style lang="stylus" scoped>
@import "~@/assets/styles/varibles.styl"
.list
    display flex
    flex-direction column
    justify-content center
    position absolute
    top 1.58rem
    right 0
    bottom 0
    width .4rem
    .item
        text-align center
        line-height .4rem
        color $bgColor
</style>